It has been shown that the active form of vitamin D3, 1,25-dihydroxyvitamin D3 (1,25(OH)2D3), has biological effects on human skin. Psoriasis is caused by abnormally rapid growth of skin cells. We have demonstrated that this vitamin D compound decreases the growth rate of normal cells in adults. We are interested in determining whether 1,25 (OH)2D3 is useful for treating psoriasis in children ages 4 through 18 years.